Consistent Operating System Servicing for Distributed Nodes

1. A computer system to deploy updated images to distributed nodes in data centers, the system comprising: a staging service configured to: initialize a virtual machine to update an existing image of an operating system using a patch, wherein the existing image is stored at the staging service as an image that corresponds to a deployed image on the nodes in a data center, the existing image having a variant state and an invariant state of the operating system; the virtual machine configured to: generate an updated image of the existing image that corresponds to the deployed image on the nodes, wherein the patch is installed on the variant state to generate the updated image at the virtual machine; and provide the updated image having the patch pre-installed, the updated image is provided to cause targeting nodes running the deployed image of the existing image used to generate the updated image; and one or more nodes configured to: receive the updated image, wherein the updated image is received at the one or more nodes running the deployed image that corresponds to the updated image generated based on the existing image and virtual machine associated with the staging service; and boot to the updated image without performing an installation of the updated image on the one or more nodes.

2. The computer system of claim 1 , further comprising a fabric controller configured to make a determination to roll out the patch to the operating system and communicate an indication to staging service to generate the updated image, wherein generating the updated patch comprises: separating, at the virtual machine of the staging service, the existing image into the variant state and the invariant state, to process the states separately; performing, at the virtual machine of the staging service, an installation of the patch on the variant state; and recombining, at the virtual machine of the staging service, the variant state and the invariant state to form the updated image, wherein the updated image functions as a new operating system of a node based on the node booting up to the update image without installation of the updated image.

3. The computer system of claim 1 , wherein the virtual machine supports the existing image having a virtual disk linked to a differencing disk, the virtual disk comprises the invariant state of the operating system and the differencing disk stores the variant state of the operating system, wherein the virtual disk and the differencing disk are configured such that a service application supported by the operating system writes data to the differencing disk and does not write data to the virtual disk.

4. The computer system of claim 1 , wherein generating the updated image at the virtual machine further comprises: mounting the existing image on the virtual machine, wherein the existing image is a pristine model of the operating system that excludes data written to the operating system when running on the one or more nodes; copying the patch to the mounted existing image; setting a command within the existing image that executes upon activating the virtual machine; activating the virtual machine to cause the command to execute to be invoked, wherein, during execution, the command instructs the existing image to install the patch; capturing a snapshot of the existing image with the patch installed; saving the snapshot as the updated image; and utilizing the updated image for upgrading the operating system of the one or more nodes.

5. The computer system of claim 1 , wherein the one or more nodes are further configured to: initiate an offline condition; download the updated image; and boot to run an operating system of the updated image without reinstalling the operating system of the updated image.

6. The computer system of claim 5 , wherein downloading the updated image further comprises the one or more nodes configured to: receive the updated image comprising an updated virtual disk and a differencing disk that is empty and cleared of externally-written data; store the updated virtual disk such that a new operating system is ready to be used upon booting; and replace a differencing disk on the one or more nodes with the differencing disk of the updated image.

7. A computer-implemented method for upgrading operating systems of computing devices, without installing patches on the computing devices, the method comprising: downloading an updated image of an existing image of operating system having a variant state and an invariant state, the updated image having a patch pre-installed using a staging service, the updated image is downloaded to cause retiring of a deployed image that corresponds to the existing image used to generate the updated image; wherein the staging service initializes a virtual machine to generate the updated image with the patch that is installed on the operating system at the virtual machine of the staging service; wherein the virtual machine supports the existing image having a virtual disk and a differencing disk, the virtual disk comprises the invariant state of the operating system and the differencing disk stores the variant state of the operating system, wherein the virtual disk and the differencing disk are configured to cause a service application supported by the operating system to write data to the differencing disk and not write to the virtual disk; booting to the operating system of the update image; and utilizing the operating system of the updated image without performing an installation of the patch.

8. The computer-implemented method of claim 7 , wherein generating the updated image at the staging service comprises: separating the existing image into the variant state and an invariant state; performing an installation of the patch on the variant state; and recombining the variant state and the invariant state to form the updated image, wherein the updated image functions as a new operating system of a node based on the node booting up to the update image without installation of the updated image.

9. The computer-implemented method of claim 7 , the method further comprising: receiving the updated image comprising an updated virtual disk and a differencing disk that is empty and cleared of externally-written data; storing the updated virtual disk such that a new operating system is ready to be used upon booting; and replacing a differencing disk on the one or more nodes with the differencing disk of the updated image.

10. The computer-implemented method of claim 7 , wherein the updated image is propagated to be downloaded based on a persistence algorithm, wherein the persistence algorithm selects an order and timing for removing one or more nodes, that download updated images, to an offline condition to ensure that active redundant nodes are available for supporting the particular functional aspects of the service application that are supported by the one or more nodes.

11. One or more computer storage hardware memory having computer-executable instructions embodied thereon that, when executed, perform a method for deploying updated images to one or more nodes propagated throughout a distributed computing platform, the method comprising: receiving an indication to install a patch to an existing image of an operating system residing on one or more nodes of a data center, wherein the existing image is stored at a staging service as an image that corresponds to a deployed image on the one or more nodes; generating the updated image by applying the patch to the existing image at a virtual machine, wherein the updated image having the patch pre-installed is communicated to cause targeting the one or more nodes running the deployed image of the existing image used to generate the updated image, the virtual machine supports the existing image having a virtual disk and a differencing disk, the virtual disk comprising the invariant state of the operating system and the differencing disk stores the variant state of the operating system; and pushing the updated image, to the one or more nodes of a data center to cause booting to the updated image at the one or more nodes, wherein the one or more nodes are configured to utilize the updated image of the operating system without performing an installation of the updated image.

12. The one or more computer storage hardware memory of claim 11 , wherein generating the updated image by applying the patch to the existing image at a virtual machine further comprises: copying the patch to the mounted existing image; and setting a command within the existing image that executes upon activating the virtual machine.

13. The one or more computer storage hardware memory of claim 11 , wherein generating the updated image by applying the patch to the existing image at a virtual machine further comprises activating the virtual machine to cause the command to execute to be invoked, wherein, during execution, the command instructs the existing image to install the patch.

14. The one or more computer storage hardware memory of claim 11 , wherein generating the updated image by applying the patch to the existing image at a virtual machine further comprises: capturing a snapshot of the existing image with the patch installed; saving the snapshot as the updated image; and utilizing the updated image for upgrading the operating system of the one or more nodes.

15. The one or more computer storage hardware memory media of claim 11 , wherein the method further comprises: separating, at the virtual machine of the staging service, the existing image into a variant state and an invariant state of the operating system, the operating system having at least one differencing disk and a virtual disk, wherein the virtual disk is a pristine model of the operating system; performing, at the virtual machine of the staging service, an installation of the patch on the variant state; and recombining, at the virtual machine of the staging service, the variant state and the invariant state to form the updated image, wherein the updated image functions as a new operating system of a node based on the node booting up to the update image.

16. The one or more computer storage hardware memory of claim 15 , wherein the virtual disk is configured to accommodate the invariant state of the operating system that is common to each of the one or more nodes of the data center.

17. The one or more computer storage hardware memory of claim 15 , wherein the at least one differencing disk is configured to accommodate the variant state of the operating system that is affected by the role instances of the service application running on the one or more nodes.

18. The one or more computer storage hardware memory of claim 15 , wherein generating the updated image by applying the patch to the existing image at a virtual machine further comprises: selecting at least one empty differencing disk based upon attributes of the one or more nodes that are targeted for receiving the updated image; and combining the at least one empty differencing disk with the virtual disk upon installing the patch thereto.

19. The one or more computer storage hardware memory of claim 18 , wherein selecting at least one empty differencing disk based upon attributes of the one or more nodes that are targeted for receiving the updated image comprises: recognizing the role instances of the service application running on the one or more target nodes; and identifying the at least one empty differencing disk that adequately supports functionality of the one or more target node.

20. The one or more computer storage hardware memory of claim 18 , wherein pushing the updated image to the one or more nodes of the data center comprises: removing the one or more nodes to an offline condition; loading the updated image to the one or more offline nodes; and booting the one or more offline nodes, wherein the process of booting does not reinstall the operating system carried in the updated image.